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    求出1-1/2+1/3-1/4…..1/100的和 var i=1;
    <script>
        var sum1 = 0;
        var sum2 = 0;
        for (var i = 1; i <= 100; i++) {
            if (i % 2 == 0) { //偶数
                sum1 = sum1 - (1 / i);
            } else if (i % 2 == 1) { //奇数
                sum2 = sum2 + (1 / i);
            }

        }
        console.log(sum1 + sum2);
    </script>
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